1. Introduction

The mammalian thalamic relay nuclei play a pivotal role in the transmission of sensory information to the cerebral cortex (Jones, 1985). It has become evident that this is not a mere relay function, but that the thalamus is a site where processing and gating of information takes place, and that this function is intimately associated with, and regulated by neural processing in the sensory cerebral cortices (Koch, 1987; Steriade & Llinas 1988; Steriade et al., 1993). Furthermore, thalamic transmission can be modulated by a number of inputs which arise from the brain stem (McCormick, 1989, 1992; Steriade et al., 1990). Central to the processing functions of the thalamus are the actions of the various neurotransmitters and modulators which can be released by the various neural and glial elements, and how these chemical messengers exert their influence, both alone and in conjunction with other transmitters (McCormick & Bal, 1994). The functional roles and identity of the transmitters released by the various afferents, intrinsic neurones, glia, and modulatory systems have been the subject of intense research over the last decade, and it is now known that a number of transmitters are utilised in these functions; for example: L-glutamate, gamma-aminobutyric acid (GABA), amines such as acetylcholine, noradrenaline and serotonin (5-HT) (McCormick, 1992).

Over recent years, there has been a mass of new work concerning the excitatory amino acid receptors (also known as glutamate receptors), which has brought to light many previously unknown receptor types and subunits: this in turn has enabled the determination of the physiological, biochemical and pharmacological properties of these receptors, and the location of the receptors on neuronal and glial structures (Gasic & Hollmann, 1992; Hollmann & Heinemann, 1994; Nakanishi 1992; Westbrook, 1994). This new knowledge has been applied to the thalamus, amongst many other brain areas, and it is this which has provided the impetus for this review of glutamate receptor function(s) in the thalamus. It is hoped that this synthesis, based on one particular brain region, will provide not only an overview of glutamate transmission in the thalamus, but also may provide new insights into the overall functioning of excitatory amino acid transmission.

NOTE Please note: this document is part of the HTML version of a paper originally published in print in Progress in Neurobiology.

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